A Heat exchanger for cooling air, which may for example be used for thermal management in an aircraft (for example a Medium Altitude Long Endurance Aircraft), has been disclosed in the Applicants earlier International Patent Application WO2012/095646, the contents of which is incorporated herein by reference.
This application discloses a heat exchanger as shown in FIG. 1. The heat exchanger 51 comprises a laminated stack of air flow channels 90 interlaced with heat sink layers 92. The heat exchanger 51 further comprises a plurality of thermoelectric devices 94 positioned between each air flow channels 90 and heat sink layers 92. The laminated stack is surrounded by an insulation jacket 96. The input to the insulation jacket/laminated stack is provided by the input 56. The output of the insulation jacket/laminated stack may feed into a water extractor 98. The output of the water extractor 98 is output 58.
In operation, input air 100 enters the heat exchanger 51 and flows (as indicated by reference numeral 102 in FIG. 1) along the air flow channels 90, then exits the airflow channels 90 as cooled output air 104. The cooled output air 104 then flows through water extractor 98 and then exits as cooled and dried output air 106. Heat is extracted from the air 102 flowing along the air flow channel 90 and transferred via the thermoelectric device 94 into the heat sink layer 92. Thus, in operation, a first surface of the thermoelectric device 94 operates as a cold face, and the other surface of the thermoelectric device operates as a hot face. An electrical current is applied across the thermoelectric device 94, thus establishing an additional temperature difference between the hot face and the cold face. By such provision and use of the thermoelectric device, the heat transfer is made more efficient. Fins are provided extending outwards into the air flow channel and heat sink layers to further render the heat transfer process more efficient.
It will be appreciated that the heat exchanger disclosed in International Patent Application WO2012/095646 is specifically arranged for cooling of a fluid (i.e. it is arranged to remove heat from a fluid passing through the heat exchanger). However, in some applications it is desirable to provide a two way heat exchange such that a first relatively hot fluid may be passed through the heat exchanger so as to be cooled while a while a second relatively cold fluid passes through the heat exchanger to be heated. Embodiments of the invention seek to provide an improved heat exchanger for such two-way heat exchange.